1. Field of the Invention
This invention relates to a lens meter used in ophthalmic hospitals, by opticians, etc., to measure the refractive value, i.e., the degree of spherical refraction, the degree of astigmatic refraction, the astigmatic angle and the degree of prism, of lenses for spectacles.
2. Related Background Art
The conventional lens meters are generally designated such that the image of a chart illuminated by a light source is formed by an auxiliary lens. The image of the chart is observed by means of a telescope adjusted to infinity through a lens to be examined. The chart is moved in the direction of the optic axis so as to enable the image of the chart to be clearly seen, and at that point of time, the position of the chart graduated in diopter is read to thereby obtain the measured value of the refractive power.
Recently, use has been made of automatic measuring lens meters of the type in which the measured value is obtained by depressing a button after manual adjustment of the lens meters. However, like popular lens meters, such lens meters are complex because of the presence of mechanically movable portions.